This PDF file contains the front matter associated with SPIE Proceedings Volume 12013, including the Title Page, Copyright information, Table of Contents and Conference Committee lists.

The MOEMS Fabry-Perot interferometer (MFPI) based hyperspectral cameras have the advantage of being low cost and highly compact, but the performance characteristics determine if particular device can be used in given application. This paper describes the performance test results of exceptionally compact cubic-inch sized VNIR hyperspectral camera. This camera prototype was developed in a project supported by European Space Agency (ESA) and its long-term goal of this project was to develop reliable, compact and lightweight hyperspectral camera for space exploration vehicles, such as drones, landers and rovers. The camera operates in 650 nm - 950 nm range and the field of view is ca. 12.5° × 10° with image size of 640 × 480 pixels. The prototype was tested for operation in space environment. This involved test in a thermal vacuum chamber as well as a vibration test. The MFPI, developed by VTT, was also separately tested in near vacuum to evaluate its actuation speed and resonance characteristics. In addition to environmental tests, the camera completed wavelength and temperature calibration. The data acquisition speed and spectral characteristics were also determined. The results of these tests and other procedures are presented in this paper.

Amplitude-modulated continuous wave (AMCW) time-of-flight (ToF) sensor is widely used to capture 3D information of objects due to its relatively high measurement precision in short range. However, the measurement accuracy of AMCW ToF measurement method is generally sensitive to the reflectivity of object, internal stray light, modulation instability, and external light. Consequently, distance measurement error inevitably occurs even in indoor measurement condition. To compensate such error, a post processing method based on machine learning is proposed in this paper. This data driven correction method is validated under indoor measurement condition. According to the experimental results, the distance measurement error correction method presented in this paper shows the most high accuracy compared to other related research results.

Robots and drones are presently in the industry’s focus to serve a critical role in Industry 4.0 and the Transportation Revolution. Integration of robots and drones in these areas improves efficiency and safety, adds flexibility in operation, and reduces operating costs. However, they are still far from achieving the optimal performance needed to execute autonomous tasks at high levels. As these platforms are battery operated, all sub-systems that augment their capabilities must be low-power solutions. In the case of airborne drones, it is also critical that solutions are ultra-light weight and of small form factor. Additionally, robots will be employed in the modern working environment in tandem with humans, but adequate human-robot interaction and intention communication solutions do not currently exist. Consequently, MEMS mirrors-based sensing and interaction systems designed for robots and drones are essential as they offer solutions with the lowest power consumption, weight, and cost in high volume. However, existing MEMS Mirror based solutions have not achieved the necessary compactness and efficiency for robotics. In this paper we describe and demonstrate MEMS Mirror-based 3D perception sensing (SyMPL 3D Lidar) and animated visual messaging (Vector Graphics Laser Projection with Playzer) systems optimized for robots and drones. These sub systems each consume <1W in power, at least 10x lower than other solutions in the market, weigh <50g, and have small form factors. Furthermore, we will show that combining these two systems leads to new capabilities and functionalities that meet the demands of robot vision and human-robot interaction.

The adoption of MEMS mirrors has been rapidly growing in recent years, involving different types of applications. One of the most challenging applications for Laser Beam Scanning (LBS) displays are Augmented Reality (AR) glasses, since they require high resolution images, small volume occupation and low power consumption. To comply with these requirements, MEMS scanners are moving to piezoelectric actuation, a technology that enables high actuation forces and high efficiency in a small die area. In this work, two compact MEMS mirrors with piezoelectric actuation are presented: a 27.5kHz resonant mirror (MMR40100) with 1.1mm diameter and 56deg FOV and a quasi-static mirror (MML40100) working at 60Hz with 2.45x1.44mm2 reflective area and 32deg FOV. The working voltage is <40V for both mirrors, keeping the power consumption low (<20mW). To enable the mirror control, diffused piezoresistive sensors in Wheatstone bridge configuration are integrated in both mirrors. In this paper it will be described the working principle of the MEMS designs, the manufacturing process, the FEM simulations and the experimental findings obtained on fabricated samples. Once coupled together, the two mirrors enable a 720p display module with 65deg diagonal FOV and a volume occupation of the entire display module of <0.7cc making this solution one of the most promising for the next-generation AR glasses.

Computer generated holography (CGH) offers the best possible solution for very interesting applications like virtual, augmented and mixed reality. To get the images from the computer into the real world, spatial light modulators (SLMs) are required that fulfil very demanding specifications. Unfortunately, none of the currently available kinds of SLMs can meet this challenge fully. Within the European Union funded Project REALHOLO we are therefore developing a novel kind of MEMS (micro electro mechanical system) SLM especially for CGH applications. The challenge is to modulate the phase of incoming coherent light with millions of individually controllable pixels. The pixels have to be only a few micrometers in size for acceptable diffraction angles and still have a stroke range of half the wavelength of visible light, about 350nm. Within this range, each pixel needs to be set very precisely to one of many deflection levels at frame rates of more than one kHz. This paper discusses the challenge and our solution: an innovative MEMS comb drive actuator array, monolithically integrated on top of a CMOS backplane. The advantages of this design are compared to other types of SLMs and its superior performance is shown by FEM simulations. We also discuss the impact of effects like charging and fabrication imperfections on the deflection precision. Our newly developed MEMS technology and SLM will also enable many other applications that may benefit from the fast and precise phase modulation by a large number of pixels, like wave front shaping or quickly re-programmable diffractive optical elements (DOEs).

Despite the high linearity of Al(Sc)N as piezoelectric actuator material, quasi-static MEMS mirrors show exemplary differences due to intrinsic stress. To control the static and dynamic behavior of the mirror, an electronic control system may be used. Rapid control prototyping (RCP) can be a helpful tool for developing generic or application-specific control schemes. This paper provides a practical introduction to the RCP approach and demonstrates it in practice with a gimbal-less bi-axial micro mirror. The application example is a long-range LIDAR system with optical positioning tolerance <0.1 degree and <400 µs point-to-point transition rate. An open loop control is implemented with a digital filter (finite-duration impulse response, FIR), using standard functions from MATLAB®/Simulink® to generate a random signal, a model of the mirror and a Gaussian filter. The response to the filtered input signal is simulated before running the control scheme on the RCP system. The modeling process relies on automatic code generation to program the RCP target system or other supported platforms.

The System-In-Package here presented manages the movement of a couple of piezoelectric mirrors used for Raster Scan Projection applications. Its partitioning consists in two dice stacked one above the other. The first die works in the High Voltage domain and is responsible of the driving of the mirrors; it includes a single coil dual output boost converter that produces high voltage supplies (up to 45V). The linear driver that works up to 42V is composed by a low voltage DAC and a rail-to-rail push-pull output amplifier. The resonant driver, implementing a charge recovery architecture, translates a low voltage pulsing signal into a synchronous high voltage trapezoidal signal that excites the resonant mirror. The second die works in the low voltage domain to sense and control the mirrors movement. The PZR Wheatstone bridge, one for each mirror, is biased with a programmable voltage. Its differential output is applied to a read-out chain composed by a programmable Analog Front-End and a Continuous-Time  A/D Converter with 16-bits resolution. A fully integrated digital block processes the signals produced by the two sensing chains that are applied to their relative control loop algorithm. An additional front-end path is present to measure the PZR Bridge working temperature for sensitivity versus temperature compensation. Innovative lock-in and opening angle algorithms allows to control the movement of the resonant mirror against temperature, pressure and aging variations. Similarly, an innovative multi feedback PID algorithm controls the linear mirror movement mainly suppressing the fundamental resonant component as well as other spurious modes.

Micro-mirror which is capable of steering light at a reasonably high speed, is an important component in MEMS solid state LiDAR systems. Longer detection range and larger field of view (FOV) are often ideal in many applications, such as autonomous driving, and those aspects can be achieved by increasing the mechanical angle of the micro-mirror as well as the size of the aperture. However, as the aperture and rotational angle (θopt⋅D) get bigger, the dynamic deformation inevitably becomes larger, thus affecting the collimation performance. One potential solution is to add a backside rib support to the mirror which can reduce the dynamic deformation while keeping its moment of inertia low. Conventional backside rib designs are primarily based on intuitive structural patterns, and the design process is time-consuming. Also, the performance improvement is based on trial and error which does not guarantee success in the end. To shed light on an optimized pattern with the focus of large θopt⋅D and low dynamic deformation, in this paper, we propose a piezoelectrically driven micro-mirror with an optimized backside rib enabled by a particle swarm optimization (PSO) algorithm and iterative FEA modeling. Experimental results show that compared with an intuitive pattern, the automatically-generated pattern can reduce the beam divergence by 30% while keeping the same moment of inertia.

The present paper on regards the improvement of the way one resonant MEMS (Micro Electro-Mechanical System) micro-mirror is usually controlled to project the wanted laser beam scanning image/pattern, with the goal of creating a fast-response application able to reach as fast as possible the wanted projection aperture and to maintain it with discrete voltage pulses, minimizing the angle amplitude error and with a look to the power consumption of the architecture. On top of that a self-adapting actuation system was realized, able to comply to any mirror design obtaining, thus, a driving system which no longer requires to be initialized according to the mirror parameters. The previous architecture, in fact, leveraged the well-known resonant frequency of the driven mirror, to set two square-wave signals with the same frequency and shifted by 180 degrees for the two mirror’s electrodes, and with a certain voltage amplitude to reach a specific aperture. This technique, otherwise, fails to ensure a fast initial opening of the mirror to get to the target angle and requires a continuous excitation during its operation time to hold the same oscillation amplitude, even more if we consider the low damping coefficient that characterize these high-Q mirrors and that, despite the benefits, makes the device less stable due to its high responsivity. For these reasons the project was born to overcome these limitations and to create a design based on larger but sporadic pulses, thinking about boosting the initial opening and controlling it without a continuous change in driving amplitude voltage. The paper will detail a first modelling of the architecture, designing with Simulink the features of the new driving system and testing them with the model of a generic resonant mirror, a various Q factor. Once the simulations results were satisfying and some design solutions were identified, will be described a RTL implementation of an architecture on an FPGA (Field Programmable Gate Array), mounted on an custom evaluation board. A discussion of experimental results will follow, to verify experimentally the stability of the architecture designs identified on a board that manages the full control of a mirror, actuating and sensing its oscillation, especially in comparison with the legacy driving mode.

This paper reports a secondary scan mirror for step-stare lidar applications that is single axis and operates in a non resonant mode. The mirror has a resonant frequency of 61 kHz and a diameter of 2 mm with angular scan range equivalent to 10 resolvable spots at 780 nm. Hand calculations and finite element simulations showed good correlation with experimental results. The mirror, which is 300 μm thick, achieves torsional motion through electrostatic force electrodes placed 3 µm beneath it. Simulations and measurements suggest that static and dynamic mirror deformation remains below the diffraction limit.

This paper reports a new two-axis water-immersible micro scanning mirror (WIMSM) using torsional and bending BoPET (biaxially-oriented polyethylene terephthalate) hinges. A micromachining-based fabrication process is developed to enable high patterning resolution and alignment accuracy and to reduce the amount of manual assembly. With a torsional hinge, the fast axis has a resonance frequency of ~300 Hz in air and ~200 Hz in water. With a bending hinge, the slow axis has a resonance frequency of 60~70 Hz in air and 20~40 Hz in water. 2D B-scan and 3D volumetric ultrasound microscopy are demonstrated by using the hybrid-hinge scanning mirror. The ability of scanning the slow axis at DC or very low frequencies allows a dense raster scanning pattern to be formed for improving both the imaging resolution and field of view.

We present a unique approach for 3D scanners using a single optomechanical component, the tunable prism-lens. We cointegrated piezoelectric actuators with a fluid chamber bounded by a movable glass window at the top and a flexible membrane at the bottom. We assembled the four bending actuators in perpendicular orientation to achieve a small footprint and attached their free ends to the top glass window with thin beam plates. Thereby, we gain a large clear aperture of 18 mm at a small footprint of only 20x20x2.5 mm3 . The actuators can independently pull or push the glass window at the four corners, leading to a fluid displacement and correspondingly deforming the membrane. A symmetric actuation of all the actuators results in a lens effect, with a tunable focal power range of + 12.5 dpt to -10.5 dpt at a response time of 3.5 ms. Conversely, asymmetric actuation results in a prism effect, with a tunable bi-directional scan angle of ± 1.5° at a response time of 2 ms. Hence, both modes can be combined to achieve a 3-dimensional scan by selective actuation. Our unique single component 3D scanner reduces the size and complexity compared to a conventional mirror-lens setup. In the paper, we present the design, fabrication process, analytical model, and optomechanical characterization.

o allow for adoption of optical spectroscopy in mobile and consumer devices, truly miniaturized, low-cost, mass producible spectrometers are needed. We present such a miniature (4mm x 3.2mm x 3.3mm) LGA packaged CMOS spectrometer in the range of 650-900nm and 720-1000nm. It leverages a wafer-level patterned spectral filter technology. The devices include diffuse optics and integrated spectral calibration and embedded corrections processor for part-to-part stable and repeatable performance across input angles and temperature with 68dB dynamic range, 5nm spectral resolution and up to 70 spectra/s. The run-time spectral corrections allow for plug-and-play operation of the sensor, without any need for recalibration in the field. The sensor enables portable spectroscopic applications in smart agriculture, anti-counterfeit, food analysis and skin sensing. For example, the combination of high sensitivity and speed of the spectrometer enables high sampling rate measurement of PPG signals and accurate measurement of heart rate and blood oxygenation (SpO₂).

In this work, we present the results of using a commercially available SLA printer for the fabrication of a range of designs of optical components. The optical properties are compared to off-the-shelf optics, including a detailed analysis of optical transmission, part uniformity and surface quality. A post-processing refinement step is introduced whose results are benchmarked against off-the-shelf polished glass lensesto exemplify sub-hundred nanometre surface roughness uniformity with minimal surface defects, and transmission properties as high as 85% at 638 nm for a 1 mm thick optical block without anti-reflection coatings

Electrostatic actuators have been widely employed in optical MEMS and adaptive optics systems. Tri-electrode electrostatic actuators that possess a perforated intermediate electrode between the MEMS and an underlying primary electrode, have been developed to reduce the needed control voltage. This configuration has previously been shown to improve the controllable range of motion of the MEMS an additional 60 - 70 % compared to a conventional parallel plate actuator. In this paper, the effect of extending the size of the primary electrode beyond the width of the MEMS device is studied. The presence of the intermediate electrode provides partial isolation for the MEMS, and results in an electric field from the extended primary electrode reaching the top surface of the MEMS. This enables a lifting force that counteracts the attraction force from below, thereby increasing the actuator’s controllable travel range. This effect is dependent on the size of the MEMS with respect to the spacing from the intermediate electrode (D₁). Finite Element Method (FEM) along with restoring spring force method (RSFM) are employed to study the actuator performance. The extended configuration is studied in a narrow MEMS device (with width 16D₁) and a very narrow device (cantilever type width 6.5D₁) to explore the travel range extension as a function of MEMS device size. The travel range before snap down of the narrow actuator with extended electrode showed an improvement of over 80% to that of a conventional electrostatic actuator, while the very narrow MEMS achieved 2.3 times more controllable travel distance.

Medical diagnostics in the health care sector rely profoundly on biochemical tests. Reliable, cheap, fast, and compact size tools for performing these tests will revolutionize the diagnostics industry, and enable these devices to be available at clinics or even at patient’s homes. One of the widely utilized diagnostic techniques is fluorescence-based tests. These tests are not limited to medical applications only, but also used in food quality inspection, water quality check, microorganism detection, protein and gene detection, and many other applications. In this paper, we propose a novel lab-on-chip module for fluorescence detection, as a miniaturized version of the common bench-top bulky plate reader. The module can detect and distinguish up to three different fluorophores efficiently. The module consists of multi-color filter sets for excitation and emission, implemented on the same substrate, along with a transparent microfluidic channel to pass the assay through, an excitation sources, and an optical detector to detect the emitted fluorescence light. The emission and excitation filters are thin-film plasmonic filters. Such filters offer high performance, high transmission, and acceptable bandwidth, with a few layers; which reduces the overall cost without compromising the performance. The overall size of the device is in the order of few centimeters. Hence, it consumes the least amount of biological assay. The design of the system allows it to be reliable, portable, user-friendly, fast, and cheap.

With the increasing demand for 3D depth information in various industrial applications, light detection and ranging (LiDAR) has been emerged as one of the solutions to measure the distance of objects. However, existing AMCW-based indirect ToF sensors have problems with measurement accuracy since the measured depth is sensitive to unwanted error sources such as ambient light, wide-band random noises, and stray light. In this paper, the effects of such stray light i.e. systematic error source are thoroughly analyzed in a cause-and-effect manner in terms of the signal’s amplitude and measured phase changes. Furthermore, a pre-compensation method to remove the effects of stray light is validated under various practical experimental conditions. According to the experimental results, the proposed pre-compensation method improves the measurement accuracy with mm-level depth error.

MEMS mirrors are at the core of miniaturized projection systems based on Laser Beam Scanning (LBS) which are involved in a wide range of applications in the field of Augmented/Mixed Reality and LiDAR. Most of these applications require at least one axis to be scanned with constant velocity by a quasi-static micromirror, which needs a good driving voltage to angle linearity. In practical implementations, electro-mechanical response of quasi-static micromirrors is strongly affected by MEMS nonlinearities which can be pure mechanical, like geometric nonlinearity, or can arise from the actuation principle, like electrostatic softening in comb-finger actuators or the hysteresis in piezoelectric actuators. As a result, the open loop response of the opening angle can significantly deviate from the ideal linear one affecting the final system performance. Piezoelectric micromirrors are becoming even more common in the current LBS-based product scenario. A proper and accurate modeling technique for handling the mirror scanning trajectory affected by piezoelectric hysteresis is needed for setting up the most appropriate control strategy. In this work, a modeling approach based on Bouc-Wen model describing the hysteretic behavior of piezoelectric MEMS mirrors is presented. Furthermore, a mono-axial quasi-static PZT actuated MEMS mirror has been investigated through a characterization phase focusing on the relation between the input driving voltage and the output scanning angle. A final validation stage with a comparison between collected data and model results is reported.

Accelerometers are one of the most widely used sensors. They are essential in many applications such as inertial measurement units (IMUs), airbags safety systems, activity monitoring in biomedical applications, and vibration analysis of industrial machinery. Some of these applications may need high immunity to Electromagnetic Interference (EMI). Optical accelerometers can provide such an advantage and usually shows better sensitivity. However, most of the previous versions involved optical fibers, which hindered their monolithic microfabrication. The few optical accelerometers suited for mass production presented previously in literature suffered from some other drawbacks, besides measuring in one direction (1D) only. In this work, we present a novel optical accelerometer that enables measurements in 3D, besides facilitating monolithic fabrication and simple assembly. The operation principle is based on power modulation technique that does not need complicated processing and achieves real-time measurements. The device consists of a light-emitting diode (LED), a quadrant photodetector and a proof mass suspended between them by springs allowing it to move along the 3-axes. When the proof mass moves due to the applied acceleration, more light will pass to some panels of the quadrant detector while others will receive less light, according to the motion direction. The sensor design, implementation scheme, mechanical simulation and optical modeling are reported. COMSOL finite element analysis (FEA) simulation shows a mechanical sensitivity exceeding 3.7µm/G. The modeling for both mechanical, optical and electrical transductions shows a total sensitivity up to 100 µA/G. The mechanical part of the device is fabricated using the SOIMUMPs process.